1. Field of the Invention
The invention has to do with carrier compositions which are used as vehicles in the manufacture of soft or hard gelatin capsules. More specifically, the invention relates to a gelatin carrier composition having thixatropic properties and substantial capacity to suspend active materials in a uniform dispersion.
2. The Related Art
Gelatin capsule products which are used for oral or suppository delivery of active agents are prepared by filling a hard or soft gelatin capsule with a carrier composition having the active agent incorporated therein. Prior art carrier compositions are either liquid at ambient temperature or they become liquid with heating and they are poured into the hard or soft capsules as a liquid. When the carrier compositions are liquid at ambient temperature, the active agents incorporated therein must be dissolved, they cannot be added at high loadings and it is difficult to maintain them in a uniform distribution within the capsule. Carrier compositions that are solid at ambient temperature require heating before they can be poured into the capsules and the heat can damage the capsule walls, reduce the activity of the active ingredient or damage other heat sensitive ingredients.
Oil based drug delivery systems for hydrophobic drugs are described in U.S. Pat. No. 5,645,856. The systems comprise a digestible oil and surfactant for dispensing the oil in vivo upon administration of the carrier system. The surfactant has hydrophilic and lipophilic components and the general composition of the system can be from 10-90% digestible oil, 10-60% hydrophilic surfactant and 5-60% lipophilic surfactant.
In U.S. Pat. No. 5,738,871, a hard gelatin capsule system is described for the delivery of fat soluble nutrients such as a fat-soluble vitamin (A, D, E or K) or an unsaturated fatty acid glyceride. Natural oils which are a mixture of fat soluble nutrients may be used in combination with a non-ionic surfactant, a gelatin softening agent and, optionally, water. The surfactant is present in an amount from 30% to 99% based on the total weight of the formulation used for filling the capsules.
Soft gelatin capsules are described in U.S. Pat. No. 4,701,327 as made by forming capsule shells with an ordinary grade gelatin dissolved in water and adjusted to pH 3.7 to 5.7 by the addition of pharmacologically acceptable acids.
The improvement of the present invention is the discovery of a vegetable oil based carrier composition which has thixatropic properties. Active agents are easily admixed with the carrier composition by stirring and high loadings of the active agents can be used to make a stable uniform dispersion within the carrier composition because the composition becomes semi-solid when stirring is stopped.
Advantages of the present invention include use of reduced labor to manufacture the carrier composition. The composition of the invention prevents separation of solid ingredients from the carrier prior to and after encapsulation and improves the stability of heat sensitive materials by eliminating or reducing the application of heat during processing. Lecithin and similar materials which retard the sealing of gelatin surfaces are not ingredients of the carrier composition of the invention and sealing problems are accordingly avoided.
The carrier composition of the present invention also permits digestive fluids to separate the active agents more rapidly from the carrier, thereby increasing the absorption of the active agents.
All of the ingredients used to make the carrier composition of the invention are food grade or pharmaceutically acceptable.
All percentages set forth herein are by weight/weight and all parts are by weight.
The carrier composition of the invention is a thixatropic carrier gel comprising a homogeneous dispersion of viscosity modifiers and surface active agents in vegetable oil. When the carrier composition is agitated, such as by slow stirring, it becomes fluid and when the agitation is stopped, it becomes a highly viscous semi-solid. Active agents are dispersed in the carrier composition during stirring and the material is then encapsulated. Because the carrier composition becomes a semi-solid when agitation ceases, the active solids are maintained in a stable uniform dispersion within the carrier.
The components of the carrier composition include from about 84% to 95% of a vegetable oil, from about 1% to 9% of a viscosity modifier and from about 1% to 15% of a surface active agent such that the total amounts to 100%.
Active agents which can be suspended in the carrier composition of the invention are generally in the form of fine powders and they include vitamins, pharmaceuticals, nutriceuticals and the like. These active agents are admixed with the carrier composition at loadings of up to about 50% incorporated solids based on the total weight of the carrier composition and the admixture is then filled into either hard or soft gelatin capsules.
The carrier composition is manufactured by admixing the ingredients. In the preferred embodiment, a dispersion of the carrier composition is manufactured by heating the vegetable oil to a temperature of from about 25xc2x0 to 35xc2x0 C., adding the surface active agent with agitation until uniformly distributed, heating the viscosity modifier to its melting point temperature plus up to about 5xc2x0 C. and then adding it slowly to the vegetable oil/surface active agent mixture with agitation, homogenizing the product and cooling to ambient temperature of about 23xc2x0 to 28xc2x0 C. A deaeration step may be employed following homogenization and before cooling to improve uniformity of the carrier composition product. The product then is ready for use as a carrier composition.
Suitable vegetable oils for use according to the invention include soybean oil, rapeseed oil, palm oil and cottonseed oil. The oils can be used individually or in blends and a preferred oil composition is soybean oil.
The viscosity modifier is food grade or pharmaceutically acceptable and preferably is selected from the group consisting of glyceryl palmito stearate and glyceryl behenate and equivalent compositions as will be apparent to those skilled in the art. Commercially available viscosity modifiers which are suitable for use according to the invention are COMPRITOL 888 ATO and PRECIROL ATO-5 available from Gattefossxc3xa9 Corp., 372 Kinderkamack Road, Westwood, N.J. 07675 USA.
The surface active agent is food grade or pharmaceutically acceptable and preferably is polyglyceryloleate and equivalent compositions as will be apparent to those skilled in the art. A commercially available surface active agent which is suitable for use according to the invention is PLUROL OLEIQUE C C 497 also available from Gattefossxc3xa9.
The carrier composition of the invention is made by heating the vegetable oil to a temperature from about 25xc2x0 C. to about 35xc2x0 C. followed by admixing the surface active agent therein to make a vegetable oil/surface active agent mixture. The viscosity modifier is melted and heated to a sufficient temperature to assure complete phase change, preferably up to about 5xc2x0 C. above its melting point, and then it is admixed with the vegetable oil/surface active agent mixture to make a product mixture. The product mixture is then homogenized using conventional equipment such as high shear rotational equipment or high pressure discharge equipment and then it is cooled to ambient temperature of about 23xc2x0 to 28xc2x0 C. to provide the carrier composition of the invention at ambient temperature. As an option, the product mixture can be deaerated following homogenizing but before cooling. Deaeration can be achieved by using vacuum in a vessel or a moving disc apparatus.
The carrier composition is an amber colored translucent semi-solid which becomes fluid when it is gently mixed. Active agents in powdered form can be admixed with the carrier composition at loadings of up to about 50% of active agent by total weight of the carrier composition/active agent mixture. There is no need to heat the carrier composition in order to incorporate the active agent. Stirring the carrier composition without heating makes it sufficiently fluid to incorporate the active agent and this is the preferred method of the invention. As an option, however, the carrier composition can be heated from about 25xc2x0 C. to about 35xc2x0 C. prior to admixing an active agent therein. The carrier composition/active agent mixture is filled into a hard or soft gelatin capsule for oral ingestion or use as a suppository. As an option, the mixture can be slightly heated to from about 25xc2x0 C. to about 35xc2x0 C. before it is filled into capsules.